I have 17 platy fry that are now in different stages of growth even though they are the same age. The four biggest are with the adults and loving life, seven are in a large breeder net waiting till the day they are released and the six smallest are in an aquarium having a fun time being small enough for the adults to eat, but happy that there are now only six fish in that aquarium. Well anyways, to the problem. One of the smallest guys has dropsy. Big belly, pine cone look, even eyes that are popping out. I did a 100% water change the day before I noticed he had dropsy. I hope his dropsy will magically go away one day, but I know that is unlikely. So I just wanted to ask if there was any way to help him. If I just leave him in a betta cup that's floating around the tank (he's in that until I can get a better isolation area for him) or put him to sleep. I have never put any medications in the water he has been in, although the tank went awhile without me cleaning it so that might have sparked it.

What should I do with my little guy? He looks a bit better today than he did yesterday, but I know most cases of dropsy are fatal so I'm not going to get my hopes up. Is there any medication that is known to help, and would using aquarium salt help? I think it might be from a bacterial infection so I'm currently doing some research on that.